Alcohol-related hospitalization associated with doubled stroke risk in atrial fibrillation

"Atrial fibrillation (AF) is the most common heart rhythm disturbance and is associated with a five-fold increased risk of ischaemic stroke," said Dr Al-Khalili. "AF is also associated with increased mortality, reduced quality of life and a higher risk of heart failure."

Treatment with oral anticoagulants reduces the risk of stroke and is recommended according to the number of stroke risk factors. Risk is estimated using the CHA2DS2-VASc score which gives points for clinical risk factors. Patients with non-valvular AF under the age of 65 and a score of 0 in men or 1 in women are considered to be at low risk for ischaemic stroke, and oral anticoagulation therapy is not indicated.

Dr Al-Khalili said: "Even if the risk for stroke is low, it is not negligible, and a number of such 'low risk' patients do present with ischaemic stroke in clinical practice and in patient registers."

The objective of this study was to assess the incidence and predictors of ischaemic stroke among low risk patients with non-valvular AF. This retrospective study included 25 252 low risk non-valvular AF patients (age 18-64) out of a total of 345 123 AF patients identified from the Swedish nationwide patient register for the period 1 January 2006 to 31 December 2012. The median age was 55 years and 72% were men.

The patient register holds information about all hospitalisations and visits to hospital-affiliated open clinics in Sweden. Socioeconomic variables were obtained from a database for health insurance and labour market studies. Information about current medication was obtained from the National Drug Register, which has information about all dispensed prescription in Sweden and is 100% complete.

During a median follow-up of five years, ischaemic stroke occurred at an annual rate of 3.4 per 1000 patient-years. The overall mortality was 7.5 per 1000 patient-years in patients without ischaemic stroke, and 29.6 per 1000 patient-years in patients who had suffered an ischaemic stroke during follow-up.

In the multivariable analysis, the only variables that remained significantly associated with an increased risk of ischaemic stroke were age (hazard ratio [HR] 1.06, 95% confidence interval [CI] 1.05-1.08, p <0.001 per incremental year) and alcohol related hospitalisation (HR 2.01, 95% CI 1.45 -- 2.79, p <0.001). Use of oral anticoagulants was associated with a lower risk of ischaemic stroke (HR 0.78, 95% CI 0.63-0.97, p= 0.027).

Dr Al-Khalili said: "Even through these patients are classified as low risk, the incidence of ischaemic stroke in our study population is neither negligible nor ignorable and it carries a relatively high mortality."

"Previous studies have shown a causal and dose-response relation between alcohol and AF," he added. "Our study found that alcohol is an independent risk factor for stroke in patients with AF. Alcohol might induce AF, leading to embolic stroke, or there could be a specific alcohol effect which causes systemic or cerebral thromboembolism. Using alcohol related hospitalisation as a proxy for alcohol abuse likely underestimates the extent of the problem, and does not allow grading of the amount of alcohol consumed."

Dr Al-Khalili concluded: "Doctors should ask their AF patients about alcohol use and advise patients to cut down if they are drinking more than is recommended. The beneficial link between oral anticoagulant use and ischaemic stroke in this low risk population without a recognised indication for these drugs needs further investigation, including the benefit to harm (bleeding) ratio."